Gardenia yellow is a product that is usually used in foods as a colorant under the category of food additive in Asian countries, especially in eastern Asian countries such as China, Japan and South Korea.
The product is the fruit extract of Gardenia jasminoides Ellis by alcohol and usually comprises more than 20 species of crocetin derivatives, mainly esters, but not a single compound. A chemical or an IUPAC name of the product is not available. Only recommended common name is applied. As the major crocetin ester, crocin is defined as a di-ester typically formed from gentiobiose and crocetin, including crocin-I (Crocetin-di-beta-D-gentiobiosyl ester), crocin-II (Crocetin-beta-D-gentiobiosyl-beta-D-glucosyl ester), crocin-III (Crocetin-mono-beta-D-gentiobiosyl ester), crocin-IV (beta-D-monoglucoside ester of monomethyl alpha-crocetin) and so on.
The molecular formulae of crocetin and crocin are C20H24O4 and C44H64O24, respectively. The formula masses of crocetin and crocin are 328.40 and 976.96, respectively. C.A.S numbers of crocetin and crocin are 27876-94-4 and 42553-65-1, respectively. The molecular structures of crocetin, crocetin ester and crocin are shown in Structures I, II, and III. Double bonds presented in the central polyene chain of crocetin and its derivative can result in the E- or Z-isomerization of the molecules. In Nature, the majority of crocetin and its derivative exist in all-E-configuration while the Z-isomer also can be found in minor amount.

Physical and Chemical Features
Gardenia yellow is a free-flowing powder that exhibits color from yellow to orange, smells a slight odor of fruit from Gardenia jasminoides E. and tastes slight bitter. The product is stable under neutral pH condition.
Gardenia yellow is freely soluble in water, slightly soluble in ethanol and insoluble in hexane. After the addition of 2 mL sulfuric acid into 0.5 g sample, sample color converted from deep blue to purple and finally to brown slowly. The pH value of 1% water solution is usually between 5.5 and 7.5. If heating temperature 101-105° applied for not less than 2 hours, it is dried to constant weight.
Raw materials to produce gardenia yellow is the fruit of Gardenia jasminoides E. Originated in Asia, very possible in southern China, Gardenia jasminoides is a tropical plant and most commonly found in southern China, Vietnam and India. Apart from wild type, the plant was cultured by Chinese very possibly since Song Dynasty (960-1279 AD), because some traditional Chinese paintings had depicted this plant since then (Keswick, M. 2003; Valder, P. 1999). This plant was introduced to Britain in 1750's. The plant was botanically described at the first time by English botanist John Ellis in 1761 (Foster, S, and Yue, C. 1992).
The plant is a shrub with dark green shiny leaves. The white flowers bloom from spring to summer and are followed by small oval fruit. Due to its shiny green leaves and fragrant flowers, it was widely cultured in gardens. As a tropical plant, it prefers warm and humid climate conditions. However, it likes indirect sunlight and shade rather than direct sunlight. It is an acidophile plant and likes acidic soils. For its better growing, farmers even had lower soil pH by vinegar (Gilman, E. F. 1999). Many cultivars have been developed.
China is the major culture base of Gardenia jasminoides E. In 2015, more than 10,000 tons of the fruits were collected from P. R. China. The collected fruits were processed following two major ways. One was for medical use and the other was for food colorant. Some varieties or cultivars with smaller fruit and higher geniposide amount are good for medical use. The other varieties or cultivars with larger fruit and lower geniposide content are better for pigment extraction. The annual outputs of medical-use and food colorant-consuming fruits were 4,000-5,000 and 6,000-7,000 tons, respectively, in 2015. The average amount of crocin from the food colorant-consuming fruits is 0.45% (W/W). The 30-32 tons of pure crocin were therefore able to be produced every year from P. R. China.
China is also the major producer of gardenia yellow. For more than 30 years, Chinese have prepared gardenia yellow from the fruit of Gardenia jasminoides E. After purification, the extract was used in foodstuffs as colorant. China, at the moment, is the largest producer of gardenia yellow in the world.
Usually, dried the fruit of Gardenia jasminoides is ground to form fine pieces. Ground pieces are extracted with 95% (V/V) alcohol (food grade). The extract is further concentrated by macro-porous resins. A spray drying is then applied to form final product, colorant powders. The final product usually has the crocin (crocetin plus 2 gentibiosides) amount of 45-55% (W/W) and geniposide amount less than 0.5% (W/W). No harmful chemicals applied in whole process. No toxic chemicals were involved in manufacturing. Most manufacturers were able to perform GMP, ISO and HACCP schemes simultaneously to guarantee the quality and safety of the final products.
The fruit extract of Gardenia jasminoides E. has been used as a yellow pigment to color clothes and foodstuffs for a long history. Apart from pigment resource, Gardenia jasminoides E. is also recognized as a traditional herb by Chinese. The fruit of the plant used be one of the most popular traditional Chinese medicines. In Chinese Pharmacopoeia (Version 2015), the fruit of Gardenia jasminoides E. was recorded as ‘Fructus Gardeniae from Gardenia jasminoides E. to have “drain fire” function and treat certain febrile conditions. Its recommended daily intake is 6-9 grams. The functional component of raw materials is geniposide. The average amount of geniposide is 3-5% (W/W). Information from Chinese Pharmacopoeia (Version 2015) indicates that a maximum daily intake of 450 mg geniposide is allowed.